Fluorescent lamp



Aug. 25, 1959 J. F. GlLMoRE FLUoREscENT LAMP Filed April 22, 1957 fav United States Patentl FLUoREscENT LAMP John F. Gilmore, Verona, NJ., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 22, 1957, Serial No. 654,294

2 Claims. (Cl. 313-109) known as preheat lamps and may be operated on singleor multi-lamp ballasts. Uncorrected single-lamp ballasts have low power factors of about 45% to 60%. Twolamp preheat ballasts are normally of the so-called leadlag variety, in which each lamp has a separate reactor, with a capacitor connected in series with one of the reactors to produce a leading current in one lamp. Such a ballast has the advantage of providing high power factor (between 90 and 100%) and decreased stroboscopic effeet with reduced auxiliary wattage loss and lower ballast cost per lamp. Since the currents of the two lamps are approximately 115 out of phase, the fluctuations in light output do not occur simultaneously and stroboscopic effect is considerably reduced. y

vThe capacitor Which is connected in series with one of the reactors is a fairly expensive item as is theiron in the reactors, and in order to decrease the cost of the leadlag circuits, the lamp ballast manufacturers' have raised the open-circuit voltage developed across theVV lead circuit. This enables a smaller capacitor to be used as well a's less iron in the lead-circuit reactor to cheapen the entire ballast. This increased voltage across the lamp' which is connected in the lead circuit, i.e., the lead lamp, has resulted in considerable instant starting ofthe lead lamp, particularly where the power supply may be subject to Voltage fluctuations;

Instant starting. of the lead lamp reduces its lif'econsi'derably as the emission material is prematurely depleted. This problem has been realized before and is thoroughly discussed in Patent No. 2,740,861 to Lake, which patent discloses a special glow-switch construction and gas lling therefor in order to overcome this problem. In actual practice the special glow switch as disclosed in this Lake patent will perform satisfactory when the open-circuit voltage is somewhat on the low side, but when the opencircuit voltage is higher than normal, as it often is, this specially-designed glow switch does not appreciably decrease the percentage of instant starts, as shown hereinafter.

It is the general object of this invention to avoid and overcome the foregoing and other diculties of and objections to the prior art by the provision of a fluorescent lamp which will operate in a lead-lag circuit without appreciable instant starting.

It is a further object to provide a lead-lag circuit and fluorescent-lamp combination wherein instant starting of the lluorescent lamp in the lead circuit is inhibited.

The aforesaid objects of the invention, and other objects which will become apparent as the description proceeds, are achieved by providing in the uorescent lamp a rice 2 gas till of argon at apressure of from 1.5 to 6 mm, mercury and preferably at a pressure of from 2.5 to 3.5 mm. Added to this argon gas fill is an additional Xenon gas ll in amount of from 0.5% to 1% by volume of the argon gas till.

For a better understanding of the invention, reference should be had to the accompanying drawing wherein:

Fig. 1 is a schematic diagram of a lead-lagcircuit incorporating the fluorescent lamps as described herein;

Fig. 2 is a graph of lamp starting voltage vs. percent by volume of Xenon additive to an argon gas lill for a fluorescent lamp as described herein;

Fig. 3 is a graph of percent lamp instant starting vs. transformer secondary open-circuit voltage, illustrating the instant starting encountered in lamps of various designs as well as the instant starting which is encountered with the improved glow switch design.

With specific reference to the form of the invention illustrated in the drawing, the lead-lag circuit which is il; lustrated in Fig. 1 may be substantially as described in the aforementionedpatent `to Lake and generally comprises an autotransformer 10 whichis connected across the power source. A first reactor 12 is connectedy to the secondary of the autotransfo'rmer and in series with a capacitor 14. A resistor 16 is connected across the capacitor 14 in order to minimize shock hazard. Thereactor 12 and series-connected capacitor 14 -are connected in series with one electrode 18 o f the so-called lead lamp 19. The other side of this lead-lamp electrode 1'8 is connected in series With a compensator 20, through the leadcircuit glow switch 22, through the other lead-lamp electrode 24y and to the other side of the autotransformer s'econdary. The lag-'lamp reactor26 is connected in series with oneof the electrodes28 of the lag-lamp 29, through the lag-circuit glow switch, throughthe other lag-lamp electrode 32 and to the other side of the autotransfoinier secondary. As is customary, capacitors 3 4 are provided across each ofthe glow switches .14 arid 30: ai1'd" across the compensator 20 in order to minimize radio interference'. Such a' design is generally standard' and the coupling" between' the reactor I2 arid the autotransform'er A10 is nor-` nially such that the voltage developed across' therea'ct I2, before the' lamp starts, is slightly"y greater ltliari the voltage developed across the reactor 26, in order that a smaller capacitor 154; may be used to'cheape'ri the ballast design, as' noted hereinbefore.

The suoreseen maps-19 and'V zaas saewrf are ef generally-standard design and each comprises a doubleended envelope' 3'6', vi/hicl1fI may" be" fabricated of glass', having operatively-disposedelectrodes. at cith end thereof. Such electrodes may cornpfise lkliri'eearthi'iide coded lamentary coils, as is Well known. These electrodes are electrically connected to the lead-lag circuit by lead conductors 38 which are sealed through 'the ends of the envelopes 36, as is customary. As is usual, a phosphor coating 40 is provided on the inner surface of each of the envelopes 36 and a small charge of mercury is contained within the envelopes 36. In accordance with the teachings herein, the yenvelopes also have provided therein a gas iilling of argon at a pressure of from 1.5 mm. to 6 mm. mercury and preferably at a pressure of from 2.5 mm. to 3.5 mm. mercury and at least the lead lamp 19 has an additive Xenon gas fill of from 0.5% to 1% by volume of the argon gas ll. At the lower end of the broad range of argon pressures, the life of the lamps tends to be short and at the higher end of the broad range of argon pressures, some difliculties may be encountered in starting under low-voltage conditions.

In Fig. 2 is shown the effect of the addition of Xenon gas to an argon gas fill for a liuorescent lamp. Fluorescent lamp gas lls of argon and Xenon are broadly known and are described in Patent No. 2,714,682 to Meister and 3 Heine, one of several references which broadly describe such an argo-Xenon gas ll. The effect of a very small percentage of a Xenon addition to an argon-gas ll for a fluorescent lamp, however, has never before been investigated or appreciated and this effect is most unusual and is quie critical with respect to the resultant starting voltage of the lluorescent lamp. Referring to Fig. 2, the starting voltage for the fluorescent lamp which incorporates an argon lill rises very sharply with the addition of verysmall amounts of xenon. At a Xenon addition of one percent by volume of the argon gas lill, the curve breaks somewhat and at a xenon addition of about two percent by volume of the argon gas lill, the curve almost levels olf. It should be noted that the curves shown in Fig. 2 were taken for the well-known 40 W. T12 type of lamp. Substantially all lead-lag circuits, where instant starting of the lead lamp constitutes a problem, are designed to operate with this type of lamp.

In order to realize an appreciable improvement in inhibiting instant starting of the lead lamp, it has been found that the instant-starting voltage of the lamp should be at least 350 volts and should not exceed 415 volts or diiiculties will be encountered in starting the lamp under low-voltage conditions of operation. To achieve such starting votlages, the percent by volume of Xenon additive to the fluorescent lamp argon till should be from 0,5% to 1%, as shown in Fig. 2.

In Fig. 3 are shown test data wherein percent instant starting is plotted vs. the autotransformer secondary opencircuit voltage. The upper curve designated A represents fluorescent lamps operated in the lead circuit and having an argon gas lill only. Curve B represents fluorescent lamps operated in a lead circuit and having an argon gas fill within the prescribed ranges and an additional Xenon gas fill of 0.5% by volume-of the argon. The curve designated C represents lamps operated in the lead circuit, which lamps have an argon gas till within the prescribed ranges and a Xenon additive of 1% by volume of the argon. The curve designated D represents lamps operated in a lead circuit, which lamps have an argon gas fill with no Xenon additive and wherein the lead circuit is provided with the improved-type glow switch as described in the aforementioned patent to Lake. As shown in these curves, the improved glow switch as described in this Lake patent causes the lead lamp to operate with a relatively small percentage of instant starts when the open circuit voltage is low, but when the open circuit voltage is somewhat on the high side, a very large percentage of instant starts is encountered. Under highvoltage operating conditions, lamps operated in the lead circuit of a lead-lag ballast, and containing an additive of 0.5 by volume of Xenon to the argon ll, have about the same performance as argon-filled lamps operated in a lead circuit which is provided with improved glow 2,901,653 fr y Y switch of Lake. As the percent by volume of xenon additive is increased, the performance of such lamps when operated in a lead circuit under high-voltage conditions is better than the performance of argon-filled lamps which are operated with the improved glow switch described in the aforementioned Lake patent, see curves C and D. As shown, the curves cross at a secondary opencircuit voltage of about 217 volts, which represents a supply voltage of about 108 volts.

While decreased instant starting of the lead lamp will be realized with such an additive xenon gas ll in the lead lamp only, it may be desirable from the practical Y standpoint to provide an additive Xenon gas till in both lead and lag lamps so that the lamps cannot be confused on installation. It should be noted that it is often simpler to provide an additive Xenon gas ll in the lead lamp than to modify the glow switches in a manner as described in t'ne aforementioned patent to Lake.

It will be recognized rthat the objects of the invention have been achieved yby providing a fluorescent lamp which can be operated in a lead circuit with a considerablyreduced percentage of instant starts,

While in accordance with the patent statutes, one bestknown embodiment of the invention has been illustrated and described in detail, it is to be particularly understood that the invention is not limited thereto or thereby.

r I claim:

l. A lluorescent lamp comprising, a phosphor-coated, double-ended and radiation-transmitting envelope, operatively-disposed electrodes positioned at the ends of said envelope, lead conductors sealed through the `ends of said envelope and electrically connected to said electrodes, a small charge of mercury within said envelope, an argon gas iill at a pressure of from 1.5 mm. to 6 mm. within said envelope, and said envelope also having an additive Xenon gas fill of from 0.5% to 1% by volume of said argon.

2. A fluorescent lamp comprising, a phosphor-coated, double-ended and radiation-transmitting envelope, operatively-disposed electrodes positioned at the ends of said envelope, lead conductors sealed through the ends of said envelope and electrically connected to. said electrodes, a small charge of mercury within said envelope, an argon gas fill at a pressure of from 2.5 mm. to 3.5 mm. within said envelope, and said envelope also having an additive Xenon gas ll of from 0.5 to 1% by Volume 0f said argon.

References Cited Vin the tile of this patent UNITED STATES PATENTS 

